Sequential parking brake assembly

ABSTRACT

An assembly includes a brake system comprising, a parking brake assembly including a first drive shaft and a second drive shaft. The assembly also includes two or more opposing brake pads, and a rotor extending between the two or more opposing brake pads. During use, the first drive shaft is moved so that a first portion of the brake pad is moved relative to the rotor. The second drive shaft is moved so that a second portion of the brake pad is moved relative to the rotor. One of the first portion of the brake pad or the second portion of the brake pad is moved relative to the rotor before the other of the first portion of the brake pad or the second portion of the brake pad is moved relative to the rotor.

FIELD

The present teachings generally relate to a parking brake, and morespecifically to a parking brake mechanism for sequentially engagingmultiple pistons against a brake pad and rotor.

BACKGROUND

The present teachings are predicated upon providing an improved parkingbrake system for a vehicle. Parking brake systems typically include oneor more brake pads that are moved against a rotor to generate a parkingbrake force necessary to restrain the vehicle from moving. The parkingbrake force may be generated by electromechanical application of apiston. On a light vehicle platform, passenger cars and light dutytrucks may include rear, single piston calipers, which can adequatelydecelerate a vehicle. In the case of a non-braking condition (i.e., whenthe vehicle is parked), a parking brake system may utilize the alreadyexisting service brake caliper structure (i.e. the single piston) torestrain movement of the vehicle. The brake pads may be moved againstthe rotor with a single electromechanical gear and a linkage (i.e., aspindle and nut assembly, for example) that is already integrated withthe service brake caliper and designed to utilize the already existingsingle piston service brake caliper.

Heavy duty full size trucks, vans and SUVs may include rear, two-pistoncalipers to decelerate the vehicle, in the case of a non-brakingcondition (i.e., when a vehicle is parked), it may be desirable to havea parking brake system that utilizes the existing service brake caliperstructure that moves the brake pads via an electromechanical gear andlinkage (i.e., a spindle and nut assembly, for example) to generate aparking brake force. It may further be desirable to provide a parkingbrake force utilizing the two existing pistons and linkages (i.e., aspindle and nut assembly, for example) on the existing rear caliper toprovide increased parking brake forces for heavy duty and full sizetruck applications, for example. The parking brake system of the presentteachings aims to utilize an existing structure of a service brakecaliper to provide a parking brake system in order to reduce and/ormaintain vehicle packaging, costs, or both.

SUMMARY

The present teachings provide an assembly, comprising a brake systemcomprising a parking brake assembly including a first drive shaft and asecond drive shaft; two or more opposing brake pads; and a rotorextending between the two or more opposing brake pads. The first driveshaft is moved so that a first portion of the brake pad is movedrelative to the rotor. The second drive shaft is moved so that a secondportion of the brake pad is moved relative to the rotor. One of thefirst portion of the brake pad or the second portion of the brake pad ismoved relative to the rotor before the other of the first portion of thebrake pad or the second portion of the brake pad is moved relative tothe rotor.

The present teachings also provide a brake assembly. The brake assemblycomprises a brake caliper including a brake pad; a parking brake systemincluding a first drive shaft; a first gear selectively engaging thefirst drive shaft and selectively disengaging the first drive shaft; asecond drive shaft; a second gear engaging the second drive shaft; and amotor gear unit engaging the first gear. The motor gear unit causes thefirst gear and the second gear to rotate in a first direction and asecond direction. The first gear selectively engages the first driveshaft so that the first drive shaft rotates with the first gear andmoves the first portion of the brake pad relative to a rotor. The firstgear selectively disengages the first drive shaft so that the firstdrive shaft does not rotate with the first gear and does not move thefirst portion of the brake pad relative to the rotor. The second gearrotates, the second drive shaft and moves the second portion of thebrake pad relative to the rotor.

The present teachings further provide a parking brake system thatutilizes an existing motor gear unit and a sequential piston applymechanism to provide the increased parking brake forces needed for heavyduty and full size truck applications in a period of time expected bycustomers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a brake assembly including a brakecaliper and a parking brake assembly in accordance with the teachingsherein;

FIG. 2 is a front view of a brake assembly including a brake caliper anda parking brake assembly in accordance with the teachings herein;

FIG. 3 is a cross-sectional view of a brake assembly including a brakecaliper and a parking brake assembly taken along line 3-3 of FIG. 2 inaccordance with the teachings herein;

FIG. 4 is a front perspective view of a sequential piston applymechanism in accordance with the teachings herein;

FIG. 5 is a rear perspective view of a sequential piston apply mechanismin accordance with the teachings herein;

FIG. 6 is an exploded front perspective view of a sequential pistonapply mechanism in accordance with the teachings herein;

FIG. 7 is an exploded rear perspective view of a sequential piston applymechanism in accordance with the teachings herein;

FIG. 8 is a front perspective view of a sequential piston applymechanism in accordance with the teachings herein; and

FIG. 9 is a rear perspective view of a sequential piston apply mechanismin accordance with the teachings herein.

DETAILED DESCRIPTION

The explanations and illustrations presented herein are intended toacquaint others skilled in the art with the invention, its principles,and its practical application. Those skilled in the art may adapt andapply the invention in its numerous forms, as may be best suited to therequirements of a particular use. Accordingly, the specific embodimentsof the present invention as set forth are not intended as beingexhaustive or limiting of The teachings. The scope of the teachingsshould, therefore, be determined not with reference to the abovedescription, but should instead be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. The disclosures of all articles and references,including patent applications and publications, are incorporated byreference for all purposes. Other combinations are also possible as willbe gleaned from the following claims, which are also hereby incorporatedby reference into this written description. The present teachings claimpriority to U.S. Provisional Patent Application No. 62/108,128, filed onJan. 27, 2015, the teachings of which are expressly incorporated byreference herein for all purposes.

The teachings herein provide a brake assembly. The brake assembly mayinclude an electromechanical parking brake system that may function tocreate a clamping force (i.e., a parking brake force). The clampingforce may be a force, which, coupled with the pad coefficient offriction, prevents rotation of a rotor, prevents movement of thevehicle, or both when the vehicle is in a stopped or parked position.The brake assembly may be an opposing brake system (i.e., a fixedcaliper brake system) or a floating brake system (i.e., a floatingcaliper).

The brake caliper may function to house the components of the brakeassembly, the electromechanical parking brake system, or both. The brakecaliper may function to provide for the movement of one or more brakepads, or, preferably, two or more brake pads relative to a rotor. Thebrake caliper may move during a brake apply (i.e., a floating caliper),or the brake caliper may be fixed so that the brake caliper does notmove during a brake apply (i.e., a fixed caliper). The brake caliper maybe connected to a knuckle or a support structure of a vehicle. The brakecaliper may include one or more motor gear units (MGU) and a parkingbrake system including one or more piston assemblies developing aclamping force sequentially (i.e. a sequential parking brake assembly).The electromechanical parking brake system, the sequential parking brakeassembly, or both may be located within a housing that may be connectedto, attached to, and/or integrally formed with the brake caliper. Thebrake caliper may include one or more support brackets (i.e. supports)configured to engage the one or more brake pads. The one or more supportbrackets may be arranged around the rotor so that one or more brake padsare located on an inboard side of the rotor and one or more brake padsare located on an outboard side of the rotor.

The rotor may cooperate with the electromechanical parking brake systemto create a friction force, a clamping force, or both. The rotor may begenerally circular and may extend through a brake caliper; may bepartially surrounded by a brake caliper; or both. Preferably, the rotorextends at least partially between or within the brake caliper so thatthe friction material of one or more brake pads faces an inboard side ofthe rotor, and the friction material of one or more brake pads faces anoutboard side of the rotor. When the electromechanical parking brakesystem is actuated, the friction material of the one or more brake padsis pushed into contact with, or caused to engage one or more sides ofthe rotor to create the clamping force so that the vehicle is restrictedor prevented from moving. When the electromechanical parking brakesystem is released or disengaged, the friction material of the one ormore brake pads is moved away from the one or more sides of the rotor torelease the clamping force so that the vehicle can move freely.

The one or more brake pads may cooperate with the brake assembly, theelectromechanical parking brake system, or both and function to create abraking force, a parking brake force, or both. The one or more brakepads may function to create a braking force, a parking brake force, orboth when moved into contact with another member (e.g., a rotor, drum,or the like). The one or more brake pads may function to convert thekinetic energy of a vehicle into thermal energy by friction. The one ormore brake pads may include one or more ears or projections, which mayengage a brake caliper, a support bracket, or both. The one or morebrake pads may move relative to the brake caliper, the support bracket,the rotor, or a combination thereof. The one or more brake pads mayinclude one or more first brake pads configured to move towards and awayfrom one side or face of a rotor (i.e., an inboard rotor face) and oneor more second brake pad configured to move towards and away from anopposing side or face of the rotor (i.e., an outboard rotor face). Whenthe brake assembly, the electromechanical parking brake system, or bothare actuated, the one or more brake pads, or portions of one or morebrake pads may be moved relative to the rotor in unison, individually,sequentially, or a combination thereof. In other words, one or morebrake pads may be moved towards or away from the rotor before one ormore brake pads are moved towards or away from the rotor. Or, a firstend of a brake pad (i.e., a leading edge) may move towards or away fromthe rotor in unison, individually, sequentially, or in a combinationthereof with a second end of the brake pad (i.e., a trailing edge). Inyet another configuration, one or more brake pads and/or one or moreends of a brake pad may initially move in unison a first distancetowards the rotor, and then one or more brake pads and/or the other endof the brake pad may continue to move towards the rotor, while the otherbrake pads and/or the other end of a brake pad do not move. The otherbrake pads and/or the other end of the brake pad may, then move towardsthe rotor once the other brake pads and/or the first end hassufficiently engaged the rotor, for example (i.e., once a partial orfull braking force, parking brake force, or both are established). Thesame movements may be true in a reverse direction, where the one or morebrake pads or portions of one or more brake pads move away from therotor to release the braking force, the parking brake force, or both.The distance that the one or more of the brake pads move, or thedistance that the ends of one or more brake pads move may vary dependingon taper wear (i.e., the tendency of the friction material of a brakepad to wear unevenly during use). In other words, during a brake apply,a leading end or edge of a brake pad may contact the rotor first and/orwith a greater force than the force of a trailing end or edge of thebrake pad contacts the rotor, which may cause the leading end or edge towear more or wear faster than the trailing end or edge. Accordingly,therefore, the leading end or edge of the brake pad may need to move agreater distance than the trailing end or edge to engage the rotor. Thesequential parking brake assembly (i.e., the sequential piston applymechanism, the first and second piston assemblies, or both) may move theleading and trailing ends of a brake pad, sequentially and/or differentvarying distances towards a rotor (and away from the rotor) to accountfor taper wear.

The one or more brake pads may include a friction material and apressure plate. The friction material may include one or morenon-metallic materials, semi-metallic materials, fully metallicmaterials, and ceramic materials. The friction material may face therotor so that when the brake pads are moved against the rotor, afriction force is created to slow, stop, and/or restrict movement of avehicle. The friction material may be slotted or include grooves. Thepressure plate may be located opposite the friction surface. One or morepiston assemblies may be in communication with the pressure plate sothat all or an end of a brake pad may be moved towards or away from therotor. For example, if multiple piston assemblies are located on eachside of the rotor, one piston assembly may be moved at a time so that afirst end or a second end of the brake pad can contact the rotor beforethe other end contacts the rotor (i.e., sequential movement).

The one or more motor gear units (MGU) may function to move the one ormore brake pads against a rotor to create a braking force, a parkingbrake force, or both. The one or more motor gear units may function todirectly or indirectly (i.e., via a linkage, a sequential piston applymechanism, a spindle and nut assembly, the like, or a combinationthereof) move the one or more piston assemblies, the one or more brakepads, or both towards and/or away from a rotor to create clamping force(i.e., a braking force, a parking brake force, or both). The one or moremotor gear units may include one or more motors. The one or more motorsmay be a DC motor. The one or more motors may be a brush motor or abrushless motor. The one or more motors may be a series wound motor, ashunt wound motor, a compound wound motor, a separately exited motor, aservomotor, or a permanent magnet motor. The one or more motor gearunits may generate a torque, which, when inputted to a lead screw and anut start assembly (i.e., a spindle and nut), is sufficient to move oneor more piston assemblies, one or more brake pads, or both relative to arotor. The one or more motor gear units may generate a torque, which,when it is input to a spindle and nut assembly, is sufficient to movethe one or more brake pads against a rotor to create a braking force, aparking brake force, or both. The one or more motor gear units inconjunction with a spindle and a nut assembly may generate a holdingforce sufficient to maintain one or more brake pads against a rotor. Theone or more motor gear units may include one or more gears that mayfunction to transfer, increase, decrease, or a combination thereoftorque generated by the motor. The one or more motor gear units may belocated within a housing. The housing may be integrally formed with thebrake caliper, removably attached to the brake caliper, or permanentlyattached to the brake caliper. The one or more motor gear units may bein communication with one or more sequential piston apply mechanisms.

The one or more sequential piston apply mechanisms may function to movethe one or more piston assemblies, the one or more brake pads, or bothtowards or away from the rotor. The one or more sequential piston applymechanisms may function to cooperate with the one or more pistonassemblies to transfer rotational force (i.e., torque) generated by themotor, the motor gear unit, or both into linear force so that one ormore pistons, piston assemblies, brake pads, or a combination thereofcan move towards or away from the rotor. The one or more sequentialpiston apply mechanisms may move the one or more piston assemblies, theends of the one or more brake pads, or both in unison, sequentially, orin a combination thereof. The one or more sequential piston applymechanisms may move one or more of the one or more piston assemblies adifferent or varying distance, the same distance, or a combination ofboth. Over time, as normal brake pad taper wear increases, the one ormore sequential piston apply mechanisms may function to move one or morepiston assemblies a different distance. For example, as a leading end ofa brake pad wears more or wears faster than a trailing end of a brakepad, the one or more sequential piston apply mechanisms may function tomove the one or more piston assembles at the leading ends of the one ormore brake pads a greater distance than the one or more pistonassemblies at the trailing edge of the one or more brake pads. The oneor more sequential piston apply mechanisms may move the one or morepiston assemblies at the same time and generally the same distance; mayinitially move the one or more piston, assemblies together and thenrestrict movement to one or more piston assemblies while one or morepiston assemblies do not move; may move one or more piston assembliesbefore moving one or more piston assemblies; and so on. The one or moresequential piston apply mechanisms may move the one or more pistonassemblies faster and greater distance (or, conversely, slower and ashorter distance) than another of the one or more piston assemblies. Thesequential piston apply mechanism may include a first gear and a secondgear.

The first gear may function to receive and transfer torque from the oneor more motor gear units to the first spindle, the second gear, thesecond spindle, the one or more piston assemblies, the one or more brakepads, or a combination thereof to move the one or more brake padsrelative to the rotor. The first gear may include a flange or an inputsplined shaft for engaging the motor gear unit so that the motor gearunit can rotate the first gear. The input splined shaft may includeteeth, splines, and/or notches engaging corresponding teeth, splines,and/or notches on the motor gear unit. The motor gear unit may engagethe input splined shaft and cause the first gear to rotate in a firstdirection, a second direction, or both. The first direction may becounterclockwise and the second direction may be clockwise, or viceversa. Both of the first and second gears may include teeth, grooves,notches, channels, or like features for interconnecting the first andsecond gears together with a belt, chain, linkage, the like, or acombination thereof. Accordingly, the second gear may rotate in thefirst direction, a second direction, or both in unison with the firstgear when the motor gear unit rotates the first gear. Relative to oneanother, the first gear and the second gear may rotate at the same speedor with different speeds. The first gear may include the same number ofteeth, grooves, notches, and/or channels as the second gear so that thefirst gear and the second gear rotate at the same speed. In other words,the ratio of teeth on the first gear to second gear may be 1:1. Thefirst gear may include more teeth, grooves, notches, and/or channelsthan the second gear so that the first gear rotates faster than thesecond gear. The first gear may include less teeth, grooves, notches,and/or channels than the second gear so that the first gear rotatesslower than the second gear, in other words, the ratio of teeth of thefirst gear to the second gear may be 1:1.05 or 1:1.1 or 1:1.2.

The first drive shaft may function to transfer torque from the motorgear unit, the first gear, or both to the one or more piston assemblies,the one or more spindles and nuts, the one or more brake pads, or boththat are in communication with the first drive shaft. The first driveshaft may include one or more detents, notches, grooves, projections, orfeatures that can be engaged by the first gear, the one or more rollerassemblies, or both. When the first drive shaft is engaged by the firstgear, the one or more roller assemblies, or both, the first drive shaftrotates with the first gear (and the second gear). The first drive shaftmay include splines, notches, grooves or teeth for engaging the one ormore piston assemblies, the one or more spindles, the one or more nuts,or a combination there to transfer torque from the motor gear unitthereto when engaged by the first gear, the one or more rollerassemblies or both so that the one or more brake pads can move relativeto the rotor. When the first drive shaft is not engaged, or isdisengaged by the first gear, the one or more roller assemblies, or boththe first drive shaft does not rotate with the first gear (or the secondgear) and may not transfer torque to the one or more spindles, nuts,pistons, or a combination thereof. The first drive shaft may bedisengaged by the first gear, the one or more roller assemblies, or bothwhen a predetermined torque has been applied or transferred from themotor gear unit to the first piston, the first brake pad, an end of thefirst brake pad (i.e., a leading or trailing end), or a combinationthereof. The predetermined torque may be greater than 1 N.m, greaterthan 5 N.m, greater than 10 N.m, preferably between 20 and 40 N.m,preferably 30 N.m, or greater than 30 N.m. The predetermined torque maybe less than 50 N.m, less than 40 N.m, preferably between 30 and 20 N.m,less than 10 N.m, or less than 5 N.m. When the first drive shaft isdisengaged by the first gear, the roller assemblies, or both, the rollerassemblies may engage a clutch plate, a clutch plate track, a track onthe first drive shaft, or a combination thereof.

The second drive shaft may function to transfer torque from the motorgear unit, the first gear, the second gear, or a combination thereof tothe one or more piston assemblies, the one or more spindles and nuts,the one or more brake pads, or a combination thereof that are incommunication with the second drive shaft. The second drive shaft may berotationally engaged by the second gear so that the second drive shaftalways rotates with the second gear (and the first gear) or may beengaged and disengaged by the second gear, the one or more rollerassemblies, or both so that the second drive shaft only rotates with thesecond gear (and the first gear) when engaged. The second drive shaftmay include one or more detents, notches, grooves, projections, orfeatures that can be engaged by the second gear, the one or more rollerassemblies, or both. The second drive shaft may include splines,notches, teeth or grooves for engaging the one or more pistonassemblies, the one or more spindles, the one or more nuts, or acombination there to transfer torque from the motor gear unit thereto sothat the one or more brake pads or ends of one or more brake pads canmove relative to the rotor. When the second drive shaft is not engaged,or is disengaged by the second gear, the one or more roller assemblies,or both the second drive shaft, does not rotate with the second gear (orthe first gear) and may not transfer torque to the one or more spindles,nuts, pistons, or a combination thereof. The second drive shaft may bedisengaged by the second gear, the one or more roller assemblies, orboth when a predetermined torque has been applied or transferred fromthe motor gear unit to the second piston, the second brake pad, an endof the brake pad, or a combination thereof. The predetermined torque maybe greater than 1 N.m, greater than 5 N.m, greater than 10 N.m,preferably between 20 and 40 N.m, preferably 30 N.m, or greater than 30N.m. The predetermined torque may be less than 50 N.m, less than 40 N.m,preferably between 30 and 20 N.m, less than 10 N.m, or less than 5 N.m.When the second drive shaft is disengaged by the second gear, the rollerassemblies, or both, the roller assemblies may engage a track on thesecond drive shaft.

The one or more roller assemblies may function to engage and disengagethe first drive shaft, the second drive shaft, or both. The one or moreroller assemblies may be any mechanism that can engage and disengage thefirst drive shaft, the second drive shaft or both. The one or moreroller assemblies may include one or more rollers connected to a pivotarm, a pivot post, or both. The one or more rollers may engage anddisengage one or more detents, notches, grooves, projections, orfeatures of the first drive shaft, the second drive shaft, or both. Oneor more biasing members (i.e., spring(s) or any suitable resilientelement(s)) may function to bias the one or more roller assemblies intoand out of engagement with first drive shaft, the second drive shaft, orboth. The one or more roller assemblies may include only a roller incommunication with the one or more biasing members that bias the rollerinto and out of engagement with the first drive shaft, the second driveshaft, or both. The one or more biasing members may engage one or morerollers and bias the one or more rollers into and out of engagement withthe detents of the first drive shaft, the second drive shaft, or both.The one or more roller assemblies may pivot about pivot posts orprojections extending from a face of the first gear, the second gear, orboth. The one or more roller assemblies may be located on a front faceof the first gear, the second gear, or both (i.e., a face facing therotor), on a second face of the first gear, the second gear, or both(i.e., a face facing away from the rotor), or may be located on bothfaces.

When the one or more roller assemblies engage the first drive shaft,torque generated by the motor gear unit may be transferred from thefirst gear, to the first drive shaft. When the one or more rollerassemblies engage the first drive shaft, the first drive shaft mayrotate with the first gear, so that the one or more piston assemblies,spindles nuts, and brake pads in communication with the first gear, thefirst drive shaft, or both can move relative to the rotor (i.e., towardsor away from the rotor). When the one or more roller assembliesdisengage the first drive shaft, the first drive shaft may not rotatewith the first gear, so that the one or more piston assemblies,spindles, nuts, or a combination thereof in communication with the firstdrive shaft, the first gear, or both do not move relative to the rotor.When the one or more roller assemblies disengage the first drive shaft,the one or more roller assemblies may engage a clutch plate, one or moretracks on the first drive shaft, or both. When the one or more rollerassemblies disengage the first drive shaft, torque generated by themotor gear unit may not be transferred to the first drive shaft, but maystill be transferred to the first gear, the second gear, and a seconddrive shaft connected to the second gear.

When the one or more roller assemblies engage the second drive shaft,torque generated by the motor may be transferred to the second driveshaft connected to the second gear. When the one or more rollerassemblies engage the second drive shaft, the second spindle may rotatewith the second gear, so that the one or more piston assemblies incommunication with the second spindle can move relative to the rotor.When the roller assemblies disengage the second drive shaft, the seconddrive shaft may not rotate with the second gear, so that the one or morepiston assemblies in communication with the second drive shaft do notmove relative to the rotor. When the one or more roller assembliesdisengage the second drive shaft, the one or more roller assemblies mayengage one or more detents on the second drive shaft. When the rollerassemblies disengage the second drive shaft, torque generated by themotor gear unit may not transferred to the second drive shaft, but maybe transferred to the first gear, the second gear, and a first driveshaft connected to the first gear.

The one or more clutch plates may function to be engaged by the one ormore roller assemblies when the one or more roller assemblies engage,disengage, or both the first drive shaft. The one or more clutch platesmay include one or more detents, grooves, channels, or features for theone or more roller assemblies to engage when the roller assembliesengage the first drive shaft. The one or more clutch plates may rotatewith the first gear and the first drive shaft when the one or moreroller assemblies engage the one or more clutch plates and the firstdrive shaft. The one or more clutch plates may rotate freely when theroller assemblies disengage the clutch plate and engage a track on theone or more clutch plates. The one or more clutch plates may rotate withthe first gear when the roller assemblies disengage the first driveshaft and the clutch plate but engage the clutch arms. The clutch armsmay extend radially from a center of the one or more clutch plates. Theroller assemblies may engage the track so that the roller assemblies areprevented from engaging the first drive shaft. The roller assemblies mayengage the track so that the second drive shaft and the second gear canrotate and move a piston assembly and therefore an end of the brake padtowards or away from a rotor without rotating the first drive shaft (andtherefore not moving the other piston assembly towards or away from therotor). The roller assemblies may engage the track when one end of abrake pad (i.e., a leading edge) is worn more or worn further than anopposing edge (i.e., a trailing edge). By engaging the clutch track, thesecond drive shaft may continue to rotate (with the motor gear unitrotating the first gear and the second gear) and move the one or morepiston assemblies, brake, pads, or an end of a brake pad until thefriction material of the brake pad engages the rotor to create theparking brake force.

The one or more piston assemblies may function to move the one or morebrake pads toward or away from the rotor. The one or more pistonassemblies may be any mechanism configured to move or assist in movingthe one or more brake pads relative to the rotor. The one or more pistonassemblies may be located entirely or at least partially within a brakecaliper. The one or more piston assemblies may function to transferrotational force from the motor gear unit, the one or more gears, theone or more spindles, nuts, or a combination thereof into linear forceto axially move the one or more brake pads relative to the rotor. Theone or more piston assemblies may be in communication with a singlebrake pad or pressure plate so that all or a portion of a brake pad canbe moved towards the rotor to create a parking brake clamp force. Forexample, if multiple piston assemblies are located on one side of therotor, one piston assembly may be moved or actuated at a time so that afirst end of the brake pad (i.e., a leading end or a trailing end)contacts the rotor before a second end of the same brake pad (i.e., atrailing end, or a leading end) contacts the rotor. The one or morepiston assemblies may include a first piston assembly and a secondpiston assembly. The first piston assembly may be disposed near a firstend of a brake pad (i.e., a leading end) and the second piston assemblymay be disposed near a second end of a brake pad (i.e., a trailing end).The, one or more piston assemblies may each include a piston, a nut, anda spindle.

The one or more pistons may function to move one or more brake padsrelative to a rotor. The one or more pistons may move towards or awayfrom the rotor along a piston axis. The one or more pistons may move inand out of a piston opening in the brake caliper. The one or morepistons may seal a piston opening in the brake caliper so that a fluidis trapped within the piston opening, the piston, or both. The one ormore pistons may have sufficient strength so that the one or morepistons can be moved with fluid, air, by an electrical device such amotor or motor gear unit, a mechanical device such as a piston and nut,or a combination thereof. One or more of the pistons may engage a singlepressure plate near a first end of the brake pad, while one or morepistons may engage the pressure plate near a second end of the brakepad. The one or more pistons may be moved towards or away from a brakepad in unison, sequentially, or both. The one or more pistons may bemoved towards or away from a brake pad sequentially so that a first endof the brake pad moves while a second end of a brake pad is not moved,and a vice versa. The one or more pistons may be moved towards or awayfrom the one or more brake pads in unison, sequentially, or both. Theone or more pistons may include a front end is may be generally flat forengaging and moving the pressure plate towards or away from the rotor,and a back end which may include a pocket that may be keyed forreceiving an actuating device, such as a linkage, a nut, a spindle, or acombination thereof. The front end of the one or more pistons may besecurely attached or coupled to the pressure plate of the brake pad, orthe front end may removeably or selectively engage the pressure plateonce the piston contacts the pressure plate. The pocket may extend atleast partially through the piston towards a generally flat portion orpocket wall. The pocket may be configured to receive and/or engage anut.

The one or more nuts may function to engage the one or more pistons sothat the one or more piston assemblies can move the one or more pistons,the one or more brake pads or both, relative to a rotor. The one or morenuts may include a first nut and a second nut. The first nut may engagea first piston located near a first end of a brake pad (i.e., a leadingend) and the second nut may engage a second piston locate near a secondend of a brake pad (i.e., a trailing end). The one or more nuts mayengage the one or more pockets with a threaded engagement, a slidingengagement, an interference engagement, a permanent engagement, aremovable engagement, a keyed engagement, or a combination thereof. Theone or more nuts may be at least partially received into the one or morepockets. A moving force may be applied to the one or more nuts to movethe one or more pistons relative to the rotor. The one or more nuts mayat least partially move relative to the pockets and the pocket wallswithout the piston and the brake pad moving relative to the rotor (i.e.,a gap may extend between the nut and the pocket walls). The gap may bebetween 0 and 3 mm, between 0 and 2mm, preferably between 0 and 1 mm,more preferably 0.5mm. For example, the nut may mechanically engage thepocket and may be moved axially within the pocket a certain distancebefore the nut engages the pocket wall to move the piston relative tobrake pad to push the brake pad towards the rotor. The one or more nutsmay rotate within the pocket, translate along an axis within the pocketor a combination thereof to advance or retract the piston, the brakepad, or both relative to the rotor. The one or more nuts may beintegrally formed with the one or more pistons. A spindle may beconnected to the nut.

The one or more spindles may engage one or both of the drive shafts andmay function to move the one or more pistons, the one or more brakepads, or both relative to a rotor. The one or more spindles may be anymechanism configured to move so that the spindles can transferrotational force from the motor gear unit, the gears, the drive shafts,or a combination thereof into linear force to move the nut, the pistonassemblies, the brake pads or a combination thereof to create a frictionforce, a braking force, a parking brake force, or a combination thereof.The one or more spindles may be at least partially received in the oneor more pockets in the one or more pistons. The one or more spindles mayinclude one or more threaded portions, teeth, notches, grooves, or acombination thereof engaging the one or more drive shafts and the one ormore nuts to assist in axially moving the one or more pistons. The oneor more spindles may include opposing ends, each of which engage the oneor more drive shafts and the one or more nuts via a threaded engagement,a friction engagement, an interference engagement, a keyed engagement,or may be coupled thereto with mechanical fasteners. The one or morespindles may threadably engage the one or more nuts, pistons, or both.For this, the one or more spindles may each include one or more threadedportions. A first spindle may threadably engage the first nut, the firstpiston, or both, and a second spindle may threadably engage the secondnut, the second piston, or both. The thread length, lead, pitch, and/orstarts may be the same between each of the one or more spindles, or maybe different. For example, the thread pitch on the first spindle may belarger (e.g., 1.6 mm per rotation) than the thread pitch of the secondspindle (e.g., 1.5 mm per rotation), or vice versa. In other words, theratio of thread pitch of the first spindle to the second spindle may be1.05:1, 1.1:1 or 1.2:1, or vice versa. A difference in thread pitch mayprovide for the first spindle to move the first nut towards the firstpiston, the first pocket wall, or both (and therefore move the first endof the brake pad towards and/or away from the rotor) faster than thesecond spindle moves the second nut towards and/or away from the secondpiston, the second pocket wall, or both (and therefore move the secondend of the brake pad towards and/or away from the rotor), or vice versa.Spindles including different or varying thread pitches may be used incombination with gears having the same number of teeth (i.e., 1:1 gearratio) or with gears having a different number of teeth (i.e., 1:1.05 or1:1.1 or 1:12 gear ratio) in order to customize, vary, and/or perfectthe speed and distance that the one or more pistons, spindles, nuts,brake pads, ends of a brake pad, or a combination thereof move relativeto a rotor.

The one or more spindles, the one or more nuts and/or the one or morepistons may be a single integrally thrilled component or mechanism. Theone or more spindles may rotate within the piston pocket; translatealong an axis within the piston pocket or a combination thereof toadvance or retract the nut, the piston, the brake pad, or a combinationthereof relative to the rotor.

FIGS. 1 and 2 illustrate a brake assembly 20. The brake assembly 20includes a brake caliper 22 and an electromechanical parking brakesystem 24. The eletromechanical parking brake system 24 includes asequential parking brake assembly 26 located in a sequential parkingbrake assembly housing 28, and a motor gear unit (MGU) 30 located in ahousing 32.

FIG. 3 further illustrates the brake assembly 20. The brake caliper 22includes a first brake pad 34 and a second brake pad 36. A rotor 37extends between the first brake pad 34 and the second brake pad 36. Thefirst brake pad 34 and second brake pad 36 each include a frictionmaterial 38 and a pressure plate 40. The sequential parking brakeassembly 26 includes a first piston assembly 46 located near a first end48 of the first brake pad 34, a second piston assembly 50 located near asecond end 52 of the first brake pad 34, and a sequential piston applymechanism 54 in communication with both the first piston assembly 46 andthe second piston assembly 50. The first piston assembly 46 includes afirst piston 56, a first nut 58, and a first spindle 60. The firstpiston 56 interfaces with the pressure plate 40 near the first end 48 ofthe first brake pad 34. The first piston 56 includes a first pocket 62with a pocket wall 63. The first nut 58 is received in the first pocket62 and threadably engages the first spindle 60.

With continued reference to FIG. 3, the second piston assembly 50includes a second piston 64, a second nut 66, and a second spindle 68,the second piston 64 interfaces with the pressure plate 40 near thesecond end 52 of the first brake pad 34. The second piston 64 includes asecond pocket 70 with a pocket wall 71. The second nut 66 is received inthe, second pocket 70 and threats ably engages the second spindle 68.

FIGS. 4 and 5 illustrate the sequential piston apply mechanism 54. Thesequential piston apply mechanism 54 includes a first gear 72 and asecond gear 74. The first gear 72 includes an input splined shaft 76with splines 78. The input splined shaft 76 is engaged by the MGU 30(FIG. 3). The MGU 30 is configured to rotate the first gear 72 in afirst direction 98 to apply the parking brake and in a second direction100 to release the parking brake. A belt or chain 80 engages teeth 82located on the first gear 72 and the second gear 74 so that the secondgear 74 rotates with the first gear 72 when the first gear 72 isrotated. A first drive shaft 84 interfaces with a pair of rollerassemblies 92 a, 92 b that are connected to the first gear 72. The firstdrive shaft 84 includes detents 90 and splines 88. The roller assemblies92 a, 92 b selectively engage the detents 90 (as shown in FIG. 4) andalso selectively disengage the detents 90. The splines 88 engage thefirst spindle 60. When the roller assemblies 92 a, 92 b engage thedetents 90, the first drive shaft 84 rotates with the first gear 72 andcauses the splines 88 and therefore the first spindle 60 to rotate.Rotation of the first spindle 60 causes the first nut 58 to linearlytravel toward the pocket wall 63 of the first piston 56 and then movethe first piston 56. Movement of the first piston 56 causes the firstend 48 of the first brake pad 34 to move towards or away from the rotor37 (See FIG. 3). When the roller assemblies 92 a, 92 b disengage thedetents 90, the first drive shaft 84 and the splines 88 do not rotatewith the first gear 72 and, accordingly, the first spindle 60 does notrotate. Thus, the first piston 56 does not move, nor does the first end48 of the first brake pad 34. A clutch plate 102 is located between thefirst gear 72 and the first drive shaft 84.

With continued reference to FIGS. 4 and 5, the second gear 74 includes asecond drive shaft 94 with splines 96. The second drive shaft 94 rotateswith the second gear 74. When the second drive shaft 94 is rotated, thesecond spindle 68, which engages the splines 96, rotates. Rotation ofthe second spindle 68 causes the second nut 66 linearly travel towardthe pocket wall 71 of the second piston 64 and move the second piston64, which therefore causes the second end 52 of the first brake pad 34to move towards or away from the rotor 37 (FIG. 3).

FIGS. 6 and 7 further illustrate the sequential piston apply mechanism54. The first gear 72 includes a projection 122 and pivot pins 104 aboutwhich the roller assemblies 92 a, 92 b move to engage and disengagedetents 90 of the first drive shaft 84. Each roller assembly 92 a, 92 bincludes a pivot arm 106 and a pivot post 108. Each pivot arm 106includes a hole 110 engaging a respective pivot pin 104. A roller 112engages each pivot post 108. The clutch plate 102 includes a throughhole 114, detents 116, clutch arms 118, and a track 120. The throughhole 114 engages the projection 122 of the first gear 72. In addition toengaging and disengaging the detents 90 of the first drive shaft 84, theroller assemblies 92 a, 92 b also engage and disengage the detents 116of the clutch plate 102. When the roller assemblies 92 a, 92 b engagethe detents 116, the clutch plate 102 rotates with the first gear 72.When the roller assemblies 92 a, 92 b disengage the detents 116, theclutch plate 102 does not rotate with the first gear 72. The first driveshaft 84 includes a blind hole 124 engaging the projection 122 of thefirst gear 72. the second drive shaft 94 includes a blind bole 128engaging the projection 126 of the second gear 74. The second gearincludes pins 130 engaging holes 132 of the second drive shaft 94.

With reference to the FIGS. 3-7, engaging the electromechanical parkingbrake system 24 will now be described. It is understood that beforeengaging the electromechanical parking brake system 24, the first nut 58and the pocket wall 63 of the first piston 56 are separated by a firstgap (not illustrated), and the second nut 66 and the pocket wall 71 ofthe second piston 64 are separated by a second gap (also notillustrated). The second gap is also understood to be larger than thefirst gap. When the electromechanical parking brake system 24 isinitially started, the MGU 30 rotates the first gear 72 in the firstdirection 98. Via the belt or chain 80, the second gear 74 also rotatesin the first direction 98. With the roller assemblies 92 a, 92 b inengagement with the detents 90 of the first drive shaft 84 and thedetents 116 of the clutch plate 102, the first drive shaft 84 and theclutch plate 102 rotate with the first gear 72 in the first direction98. With the first drive shaft 84 engaging with the first spindle 60 viathe splines 88, the first spindle 60 also rotates and moves the firstnut 58 towards the pocket wall 63 of the first piston 56 to so that thefirst gap is taken up. At the same time, rotation of the second gear 74in the first direction 98 causes the second drive shaft 94 to rotate.Because the second drive shaft 94 is engaged with the second spindle 68via the splines 96, the second spindle 68 also rotates and moves thesecond nut 66 towards the pocket wall 71 of the second piston 64 so thatthe second gap is taken up. After the first gap is taken up, and thefirst drive shaft 84 continues to rotate and move the first nut 58against the pocket wall 63 of the first piston 56, the first piston 56moves and pushes the first end 48 of the first brake pad 34 against therotor 37 and begins to generate a clamp load. Because the second gap islarger than the first gap, the second gap continues to be reduced whileclamp load is generated as the first piston 56 pushes the first end 48of the first brake pad 34 against the rotor 37. Accordingly, a majorityof the torque generated by the MGU 30 can be transmitted to the firstspindle 60 to pushes the first brake pad 34 against the rotor 37 whilethe second spindle 68 continues to reduce the second gap between thesecond nut 66 and the pocket wall 71 of the second piston 64. Once theMGU 30 has transmitted a predetermined torque to the first piston 56(i.e., once the first piston 56 has pushed the first end 48 of the firstbrake pad 34 sufficiently against the rotor 37), the roller assemblies92 a, 92 b disengage the detents 90, 116 so that the first drive shaft84 and the clutch plate 102, respectively no longer rotate with thefirst gear 72. As the MGU 30 continues to rotate the first and secondgears 72, 74, torque is no longer transmitted to the first drive shaft84. Instead, the torque is transmitted to the second drive shaft 94while the remaining second gap between the second nut 66 and the pocketwall 71 of the second piston 64 continues to be reduced. Once the secondgap is eliminated, the torque is transmitted to the second drive shaft94 to move the second piston 64 against the pressure plate 44 to pushthe second end 52 of the first brake pad 34 against the rotor 37.

While the roller assemblies 92 a, 92 b are disengaged from the detents90, 116, the roller assemblies 92 a, 92 b contact the track 120 of theclutch plate 102. As the MGU 30 continues to rotate and the second end52 of the first brake pad 34 is pushed against the rotor 37, the rollerassemblies 92 a, 92 b may contact the clutch arms 118. In the case thatthe roller assemblies 92 a, 92 b contact the clutch arms 118, the clutchplate 102 will once again minimally rotate minimally with the first gear72 until the second piston 64 has sufficiently pushed the second end 52of the first brake pad 34 against the rotor 37 to a target force atwhich time electrical power to the MGU 30 is stopped.

The case described above is when the first end 48 and second end 52 ofthe first brake pad 34 are essentially the same thickness, whichnormally occurs when the first brake pad 34 and second brake pad 40 arenew. Over time, however, the second end 52 of the first brake pad 34(i.e., the leading end) may wear more than the first end 48 (i.e., thetrailing end), which may require the second piston 64 and the second end52 of the first brake pad 34 to move a greater distance to engage therotor 37. This is known in the art as tangential taper or taper wear. Inthis regard, the distance that the second end 52 or the leading end ofthe first brake pad 34 must move to engage the rotor 37 may continuouslychange and become larger as second end 52 wears. To account fortangential, taper, especially in braking applications including twopiston assemblies, engaging larger and/or elongated brake pads, whilethe roller assemblies 92 a, 92 b are disengaged from the detents 90 ofthe first drive shaft 84, the roller assemblies 92 a, 9 b roll along thetrack 120 and then contact the clutch arms 118 so that the clutch plate102 rotates with the first gear 72 while the first drive shall 84 isstationary. As clutch plate 102 rotates, the detents 116 on clutch plate102 rotate and begin to rotate away from the detents 90 on the firstdrive shaft 84 that were aligned with at the start of the parking brakeapply, and begin to partially alien with the next set of detents 90 onthe first drive shaft 84. Accordingly, the second piston 64 can move thesecond end 52 of the first brake pad 34 against the rotor 37 until asufficient parking brake force is realized and the MGU 30 is stopped.Stated another way, while the second piston 64 moves the second end 52of the first brake pad 34 against the rotor, the roller assemblies 92 a,92 b engage the arms 118 and rotate the clutch plate 102 and thus thedetents 116. Once the second piston 64 moves the second end 52 of thefirst brake pad 34 against the rotor 37 and a sufficient parking brakeforce is realized, the MGU 30 is stopped.

To manage a reverse taper condition, where, for example, the first end48 (i.e., the leading end) of the first brake pad 34 wears more, orfaster, than the second end 52 (i.e., the trailing end), the number ofteeth 82 on the first gear 72 may be less than the number of teeth 82 onthe second gear 74. Accordingly, when the MGU 30 rotates the first gear72 (and therefore the second gear 74 by means of the belt or chain 80),the second gear 74 may rotate slightly slower than the first gear 72,thus allowing the first piston assembly 46 and the first end 48 of thefirst brake pad 34 more time to engage the rotor 37. Additionally, oralternatively the thread pitch on the first spindle 60 may be largerthan the thread pitch on the second spindle 68 so that when the 30rotates the first gear, the second nut 66 may advance slightly slowertoward the second piston 64 than the first nut 58 advances toward thefirst piston 56, allowing the first piston assembly 46 and the first end48 of the first brake pad 34 more time to engage the rotor 37.

With reference to the FIGS. 3-7, disengaging the electromechanicalparking brake system 24 will now be described. Before disengaging theelectromechanical parking brake system 24, it is understood that thefirst piston 56 and the second piston 64 are generally in contact withthe pressure plate 44 the friction surface 38 of the first brake pad 34is generality in contact with the rotor 37; and the roller assemblies 92a, 92 b are disengaged from the detents 90, 116 of the first drive shaft84 and the clutch plate 102, respectively (i.e., the roller assemblies92 a, 92 b are in contact with clutch arms 118, and the detents 116 maybe partially aligned with a set of detents 90, due to clutch plate 102rotation in response to tangential taper). Once the electromechanicalparking brake system 24 is disengaged, the MGU 30 may rotate the firstgear 72 and the second gear 74 in the second direction 100. Because theroller assemblies 92 a, 92 b are disengaged from the detents 90 of thefirst drive shaft 84 and are located on the track 120 of the clutchplate 102, the torque from the MGU is only to the second drive shaft 94.Accordingly, the second piston 64 can move the second end 52 of thefirst brake pad 34 away from the rotor 37. As the first and second gears72, 74 rotate in the second direction 100, the roller assemblies 92 a,92 b rotate along the track 120 away from the clutch arms 118 until theroller assemblies 92 a, 92 b engage the detents 116 of the clutch plate102 and the detents 90 in the first drive shaft 84. At this time, thesecond piston 64 is no longer applying clamp load force on the secondend 52 of the first brake pad 34. Thereafter, only minimal torque isnecessary to rotate second gear 74. Once the roller assemblies 92 a, 92b engage the details 90 of the first drive shaft 84, the torque from theMGU 30 can be transmitted to the first drive shaft 84 so that the firstend 48 of the first brake pad 34 is moved away from the rotor 37.

FIGS. 8 and 9 illustrate the sequential piston apply mechanism 54. Thesequential piston apply mechanism 54 includes a first gear 72 and asecond gear 74. The first gear 72 includes an input slimed shaft 76 withsplines 78. The input splined shaft 76 is in communication with the MGU30 (FIG. 3). The MGU 30 is configured to rotate the first gear 72 in afirst direction 98 and a second direction 100. A belt or chain 80engages teeth 82 located on the first gear 72 and the second gear 74 sothat the second gear 74 rotates with the first gear 72 when the firstgear 72 is rotated by the MGU 30.

A first drive shaft 284 is connected to the first gear 72. The firstdrive shaft 284 includes detents 90. A pair of roller assemblies 92 a,92 b engage and disengage the detents 90. When the roller assemblies 92a, 92 b engage the detents 90, the first drive shaft 284 rotates withthe first gear 72 and causes the first spindle 60 to rotate. Rotation ofthe first spindle 60 causes the first nut 58 to move the first piston56, which therefore causes the first end 48 of the first brake pad 34 tomove towards or away from the rotor 37 (See FIG. 3). When the rollerassemblies 92 a, 92 b disengage the detents 90 and instead engage atrack 292 on the first drive shaft 284, the first drive shaft 284 doesnot rotate with the first gear 72, and, thus, the first spindle 60 doesnot rotate. As such, the first piston 56 does not move, and accordingly,the first end 48 of the first brake pad 34 is not moved relative to therotor 37.

A second drive shaft 294 is connected to the second gear 74. The seconddrive shaft 294 includes detents 296. A pair of roller assemblies 92 c,92 d are configured to engage and disengage the detents 296. When theroller assemblies 92 c, 92 d engage the detents 296, the second driveshaft 294 rotates with the second gear 74 and causes the second spindle68 to rotate. Rotation of the second spindle 68 causes the second nut 66to move the second piston 64, which therefore causes the second end 52of the first brake pad 34 to move towards or away from the rotor 37 (SeeFIG. 3). When the roller assemblies 92 c, 92 d disengage the detents 296and engage the track 298, the second drive shaft 294 does not rotatewith the first and second gears 72, 74, and the second spindle 68 doesnot move. As such, the second piston 64 does not move, and accordingly,the second end 52 of the first brake pad 34 is not moved relative to therotor 37.

With continued reference to FIGS. 8 and 9, the sequential piston applymechanism 54 is configured so that both gears 72, 74 initially rotate atthe same time and move the first end 48 and the second end 52 of thebrake pad 34 towards the rotor 37 at the same time until the rollerassemblies 92 c, 92 d disengage the detents 296 on the second driveshaft 294 (i.e., once a first torque has been applied to the seconddrive shaft 294). Once the roller assemblies 92 c, 92 d disengage thedetents 296, the roller assemblies 92 c, 92 d roll along a track 298 onthe second drive shaft 294 so that the second drive shaft 294 does notrotate. With the roller assemblies 92 a, 92 b continuing to engage thedetents 90 of the first drive shaft 284, the first drive shaft 284continues to rotate with the first gear 72 so that the first end 48 ofthe first brake pad 34 continues to move towards the rotor 37. Once thefirst end of the first brake pad 34 has sufficiently engaged the rotor,the roller assemblies 92 a, 92 b disengage the detents 90 and engage thetrack 292 on the first drive shaft 284. At that time, the rollerassemblies 92 c, 92 d may be generally close to the end of the track 298of the second drive shaft 294. The roller assemblies 92 c, 92 d thenre-engage the detents 296 so that the second drive shaft 294 once againcan continue to move the second end 52 of the brake pad 34 until thesecond end 52 has sufficiently engaged the rotor 37.

Any numerical values recited herein include all values from the lowervalue to the upper value in increments of one unit provided that thereis a separation of at least 2 units between any lower value and anyhigher value. As an example, if it is stated that the amount of acomponent or a value of a process variable such as, for example,temperature, pressure, time and the like is, for example, from 1 to 90,preferably from 20 to 80, more preferably from 30 to 70, it is intendedthat values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. areexpressly enumerated in this specification. For values which ate lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application in a similar manner.

Unless otherwise stated, all ranges include both endpoints and allnumbers between the endpoints. The use of “about” or “approximately” inconnection with a range applies to both ends of the range. Thus, “about20 to 30” is intended to cover “about 20 to about 30”, inclusive of atleast the specified endpoints.

The disclosures of all articles and references, including patentapplications and publications, are incorporated by reference for allpurposes. The term “consisting essentially of” to describe a combinationshall include the elements, ingredients, components or steps identified,and such other elements ingredients, components or steps that do notmaterially affect the basic and novel characteristics of thecombination. The use of the terms “comprising” or “including” todescribe combinations of elements, ingredients, components or stepsherein also contemplates embodiments that consist essentially of theelements, ingredients, components or steps. By use of the term “may”herein, it is intended that any described attributes that “may” beincluded are optional.

Plural elements, ingredients, components or steps can be provided by asingle integrated element, ingredient, component or step. Alternatively,a single integrated element, ingredient, component or step might bedivided into separate plural elements, ingredients, components or steps.The disclosure of “a” or “one” to describe an element, ingredient,component or step is not intended to foreclose additional elements,ingredients, components or steps.

It is understood that the above description is intended to beillustrative and not restrictive. Many embodiments as well as manyapplications besides the examples provided will be apparent to those ofskill in the art upon reading the above description. The scope of theteachings should, therefore, be determined not with reference to theabove description, but should instead be determined with reference tothe appended claims, along with the full scope of equivalents to whichsuch claims are entitled. The disclosures of all articles andreferences, including patent applications and publications, areincorporated by reference for all purposes. The omission in thefollowing claims of any aspect of subject matter that is disclosedherein is not a disclaimer of such subject matter, nor should it beregarded that the inventors did not consider such subject matter to bepart of the disclosed inventive subject matter.

1. A brake system comprising: a first brake piston; a second brakepiston; and a brake pad; wherein the first brake piston is moved so thata first portion of the brake pad is moved relative to a rotor, whereinthe second brake piston is moved so that a second portion of the brakepad is moved relative to the rotor, and wherein either the first brakepiston or the second brake piston is moved before the other of the firstbrake piston or the second brake piston is moved relative to the rotor.2. The brake system of claim 23, wherein the brake includes: i. a firstgear that engages the first drive shaft and disengages the first driveshaft; ii. a second gear that engages the second drive shaft; and iii. amotor gear unit in communication with the first gear and causing boththe first gear and the second gear to rotate; wherein the first gearengages the first drive shaft so that the first drive shaft rotates withthe first gear and moves the first portion of the brake pad relative tothe rotor, wherein the first gear disengages the first drive shaft sothat the first drive shaft does not rotate with the first gear and doesnot move the first portion of the brake pad relative to the rotor, andwherein the second gear rotates the second drive shaft and moves thesecond portion of the brake pad relative to the rotor.
 3. The brakesystem of claim 2, wherein the motor gear unit rotates the first gear ina first direction and in a second direction, wherein when the motor gearunit rotates the first gear in the first direction and the first gearengages the first drive shaft, the first drive shaft moves the firsttowards the rotor to create a brake force or a parking brake force,wherein the second drive shaft moves the second brake piston, which movethe second portion of the brake pad towards the rotor to create thebrake force or the parking brake force when the motor gear unit rotatesthe first gear in the first direction regardless if the first gearengages or disengages the first drive shaft, wherein when the motor gearunit rotates the first gear in the second direction and the first gearengages the first drive shaft, the first drive shaft moves the firstbrake piston which moves the first portion of the brake pad away fromthe rotor to release the brake force on the parking brake force, andwherein the second drive shaft moves the second brake piston which movesthe second portion of the brake pad away from the rotor to release thebrake force or the parking brake force when the motor gear unit rotatesthe first gear in the second direction regardless if the first gearselectively engages or disengages the first drive shaft.
 4. (canceled)5. (canceled)
 6. (canceled)
 7. (canceled)
 8. A brake assembly including:a brake pad: a first brake piston; a second brake piston a first driveshaft in communication with the first brake piston; a first gear thatdisengages the first drive shaft and the first shaft; a second driveshaft in communication with the second brake piston; a second gearengaging the second drive shaft; and a motor gear unit engaging thefirst gear and causing both the first gear and the second gear to rotatein a first direction and a in second direction; wherein when the firstgear engages the first drive shaft, the first drive shaft rotates withthe first gear, which causes the first brake piston to move a firstportion of the brake pad relative to a rotor, wherein when the firstgear disengages the first drive shaft, the first drive shaft does notrotate with the first gear and the first brake piston does not move thefirst portion of the brake pad relative to the rotor, and wherein thesecond gear rotates the second drive shaft so that the second brakepiston is moved, which moves a second portion of the brake relative tothe rotor.
 9. The brake assembly of claim 26, wherein when the motorgear unit rotates the first gear in the first direction and the firstgear engages and first drive shaft, the first drive shaft moves thefirst brake piston which moves the first portion of the brake padtowards the rotor to create a brake force or a parking brake force, andwherein the second drive shaft moves the second brake piston, whichmoves the second portion of the brake pad towards the rotor to createthe brake force or the parking brake force when the motor gear unitrotates the first gear in the first direction regardless if the firstgear selectively engages or disengages the first drive shaft, whereinwhen the motor gear unit rotates the first gear in the second directionand the first gear engages the first drive shaft, the first drive shaftmoves the first brake piston which moves the first portion of the brakepad away from the rotor to release the brake force on the parking brakeforce, and wherein the second drive shaft moves the second brake pistonwhich moves the second portion of the brake pad away from the rotor torelease the brake force or the parking brake force when the motor gearunit rotates the first gear in the second direction regardless if thefirst gear selectively engages or disengages the first drive shaft. 10.(canceled)
 11. The brake assembly of claim 8, wherein the first gearincludes one or more roller assemblies and the first drive shaftincludes detents, wherein the one or more roller assemblies rotate withthe first gear and selectively engage the detents so that the firstdrive shaft rotates with the first gear and moves the first portion ofthe brake pad relative to the rotor, and wherein the one or more rollerassemblies selectively disengage the detents so that the first driveshaft does not rotate with the first gear and does not move the firstportion of the brake pad relative to the rotor.
 12. The brake assemblyof claim 11, wherein the parking brake system includes a clutch platelocated between the first gear and the first drive shaft, the clutchplate includes a track and one or more detents, wherein the one or moreroller assemblies engage the detents of the clutch plate when the one ormore roller assemblies engage the detents of the first drive shaft, andwherein the one or more roller assemblies engage the track when the oneor more roller assemblies disengage the detents of the first driveshaft.
 13. The brake assembly of claim 11, wherein each of the rollerassemblies include: i. a pivot arm pivoting about a pin located on thefirst gear; ii. a pivot post connected to the pivot arm; iii. and aroller engaging the pivot post, wherein the pivot arm is biased so thatthe roller engage the detents of the first drive shaft when the pair ofroller assemblies selectively engage the detents and pivots about thepin to disengage the detents when the pair of roller assembliesselectively disengage the detents.
 14. A method of applying a brakecomprising: applying a torque to a first drive shaft so that the firstdrive shaft rotates and moves a first brake piston towards a rotor;rotating a second drive shaft so that a second brake piston is movedtowards the rotor, wherein either the first brake piston or the secondbrake piston is moved towards the rotor before the other of the firstbrake piston or the second brake piston is moved towards the rotor. 15.The method of claim 27, wherein the step of engaging the first driveshaft includes: biasing one or more roller assemblies into one or moredetents located on the first drive shaft, wherein the step ofdisengaging the first drive shaft includes biasing the one or moreroller assemblies out of one or more detents located on the first driveshaft, and wherein the step of the biasing the one or more rollerassemblies out of the one or more detents located on the first driveshaft includes engaging rollers of the one or more roller assembliesonto a circular track.
 16. (canceled)
 17. (canceled)
 18. (canceled) 19.(canceled)
 20. (canceled)
 21. The brake system of claim 1, wherein thebrake system comprises a single motor that moves both the first brakepiston and the second brake piston relative to the rotor.
 22. The brakesystem of claim 1, wherein the brake system comprises: a motor; a firstnut and a first spindle in communication with the first brake piston; asecond nut and a second spindle in communication with the second brakepiston; wherein during a brake apply, the motor causes the first spindleto rotate, which causes the first nut to move axially, which causes thefirst brake piston to move the first portion of the brake pad towardsthe rotor; and wherein during the brake apply, the motor causes thesecond spindle to rotate, which causes the second nut to move axially,which causes the second brake piston to move the second portion of thebrake pad towards the rotor.
 23. The brake system of claim , wherein thebrake system comprises: a first nut and a first spindle in communicationwith the first brake piston; a first drive shaft in communication withthe first spindle; a second nut and a second spindle in communicationwith the second brake piston; a second drive shaft in communication withthe second spindle; wherein when the first drive shaft is engaged,rotation of the first drive shaft causes the first spindle to rotate,which causes the first nut to move the first brake piston, wherein whenthe first drive shaft is disengaged, the first spindle is not rotatedand the first brake piston is not moved, the first brake piston is notmoved when the first drive shaft is disengaged regardless if the firstdrive shaft is rotated, and wherein rotation of the second drive shaftcauses the second spindle to rotate, which causes the second nut to movethe second brake piston.
 24. The brake system of claim wherein the brakesystem comprises: a single motor; a first drive shaft in communicationwith the first brake piston; a second drive shaft in communication withthe second brake piston; wherein when the first drive shaft is engaged,rotation of the first drive shaft by the single motor causes the firstbrake piston to move, wherein when the first drive shaft is disengaged,the first brake piston is not moved regardless if the first drive shaftis rotated by the single motor, and wherein rotation of the second driveshaft causes the second brake piston to move.
 25. The brake assembly ofclaim 8, wherein the motor gear unit comprises a single motor thatcauses both the first gear and the second gear to rotate in the firstdirection and in the second direction.
 26. The brake assembly of claim8, wherein the brake system comprises: a first nut and a first spindlein communication with the first brake piston, the first drive shaft isin communication with the first spindle; a second nut and a secondspindle in communication with the second brake piston, the second driveshaft is in communication with the second spindle; wherein after thefirst gear engages the first drive shaft, rotation of the drive shaftcauses the first spindle to rotate, which causes the first nut to movethe first brake piston, wherein after the first gear disengages thefirst drive shaft, the first spindle is not rotated regardless if thefirst drive shaft is rotated, and wherein rotation of the second driveshaft causes the second spindle to rotate, which causes the second nutto move the second brake piston.
 27. The method of claim 14, wherein thebrake includes a single motor that rotates the first drive shaft and thesecond drive shaft.
 28. The method of claim 14, wherein the methodincludes a step of engaging the first drive shaft before the step ofapplying the torque to the first drive shaft, the method includesanother step of disengaging the first drive shaft after a predeterminedtorque is applied to the first drive shaft.
 29. The method of claim 28,wherein the method includes a step of rotating the second drive shaftafter the first drive shaft is disengaged so that a second portion ofthe brake pad is moved towards the rotor.
 30. The method of claim 14,wherein rotating the first drive shaft causes a first spindle to rotatewhich causes a first nut to move, and movement of the first nut causesthe first brake piston to move a first portion of a brake pad towardsthe rotor to create a brake force, and wherein rotating the second driveshaft causes a second spindle to route which causes a second nut tomove, and movement of the second nut causes the second brake piston tomove a second portion of the brake pad towards the rotor to create thebrake force.